1. Technical Field
The present invention relates to a liquid crystal device, a manufacturing method of the liquid crystal device, and an electronic apparatus equipped with the liquid crystal device.
2. Related Art
There has been known a liquid crystal device that displays an image with the use of liquid crystal. Such a liquid crystal device may be a transflective liquid crystal device which has both functions of transmissive display utilizing illumination light by an illumination unit like a backlight and of reflective display utilizing reflection light of ambient light like natural light or room light.
Such a liquid crystal device includes a liquid crystal panel and the backlight as the illumination unit. The liquid crystal panel has a display region provided with a plurality of pixels, and a scanning line drive circuit and a data line drive circuit which are provided in the periphery of the display region for driving the pixels.
The liquid crystal panel includes an element substrate on which thin film transistors (hereinafter, referred to as TFTs) as switching elements are arranged corresponding to the pixels, a counter substrate opposing the element substrate, and liquid crystal as electro-optic material interposed between the element substrate and the counter substrate.
The element substrate includes a plurality of scanning lines provided at predetermined intervals; a plurality of data lines substantially perpendicular to the scanning lines, the data lines provided at predetermined intervals; a plurality of common lines substantially parallel to the scanning lines, the common lines and the scanning lines alternatively arranged; and the TFTs and pixel electrodes provided corresponding to the intersections of the scanning lines and the data lines, respectively.
The counter substrate includes common electrodes opposing the pixel electrodes, and a plurality of color filters for multiple colors provided corresponding to the pixels. The common electrodes provided on the counter substrate are electrically connected to the common lines provided on the element substrate through a conductive portion arranged between the element substrate and the counter substrate.
Each pixel includes a storage capacitor with an end thereof electrically connected to the pixel electrode, in addition to the TFT, the pixel electrode, and the common electrode.
A gate of the TFT is connected to the scanning line, a source of the TFT is connected to the data line, and a drain of the TFT is connected to the pixel electrode and to the storage capacitor.
In addition, the pixel includes a region for the transmissive display (hereinafter, referred to as a transmissive region), and a region for the reflective display (hereinafter, referred to as a reflective region). The above-described TFT and storage capacitor have light-shielding properties and are provided in the reflective region, while the pixel electrode and the common electrode are transparent and are provided over the transmissive region and the reflective region.
A liquid crystal thickness adjustment layer for adjusting the thickness of a liquid crystal layer, and a reflection film for reflecting incident light are formed in the reflective region.
The above-described liquid crystal device operates as follows. Application of a selected voltage from the scanning line drive circuit to the scanning lines in a line-sequential manner selects all pixels associated with a certain scanning line. Then, image signals are supplied to the data lines from the data line drive circuit simultaneously with the selection of the pixels. Owing to this, the image signals are supplied from the data lines through the TFTs to the pixels selected by the scanning line drive circuit and the data line drive circuit, whereby image data is written in the pixel electrodes.
Upon writing the image data in the pixel electrodes, a driving voltage is applied to the liquid crystal due to the potential difference between the voltage applied to the pixel electrodes and that applied to the common electrodes. That is, the voltage levels of the image signals are varied to vary the orientation and the order of the liquid crystal, so as to provide a display with gray scales according to optical modulation of the pixels.
Here, in an environment with insufficient ambient light, the transmissive display is performed with the use of the light from the backlight. That is, the light emitted from the backlight passes through the element substrate, the liquid crystal layer and the counter substrate, and then is emitted from the liquid crystal panel.
On the other hand, in an environment with sufficient ambient light, the reflective display is performed. That is, the ambient light incident from the outside passes through the counter substrate and the liquid crystal layer, is reflected by the reflection film, passes through the liquid crystal layer and the counter substrate again, and then is emitted from the liquid crystal panel.
Incidentally, according to the above-described liquid crystal device, the driving voltage which is applied to the liquid crystal is held by a storage capacitor, which is for instance configured as follows (refer to JP-A-2004-85918).
To be more specific, the scanning line and a pixel-potential-side capacitance electrode of the storage capacitor are formed on the element substrate. An insulation layer is formed on the scanning line and the pixel-potential-side capacitance electrode of the storage capacitor. The data line and a common-potential-side capacitance electrode of the storage capacitor are formed on the insulation layer.
The above-described storage capacitor includes the two oppositely arranged capacitance electrodes of the common-potential-side capacitance electrode of the storage capacitor and the pixel-potential-side capacitance electrode of the storage capacitor. These two electrodes are made of light-shielding materials. Due to this, the storage capacitor is disposed in the reflective region for ensuring aperture ratio.
The storage capacitor needs to ensure a sufficient capacity such that the driving voltage which is applied to the liquid crystal can be held. The capacity of the storage capacitor is in proportion to the areas of the two capacitance electrodes, while being in inverse proportion to the gap therebetween. Accordingly, as a method for increasing the capacity of the storage capacitor, the areas of the two capacitance electrodes may be increased, or the gap between the two capacitance electrodes may be decreased.
However, the increase in the areas of the two capacitance electrodes may cause the capacitance electrodes to extend beyond the reflective region and thus be exposed to the transmissive region, thereby degrading the aperture ratio.
Also, the decrease in the gap between the two capacitance electrodes, i.e., decreasing the thickness of the insulation layer provided between the two capacitance electrodes, results in that the scanning line is arranged close to the data line, thereby increasing the influence of cross talk on the intersection of the scanning line and the data line.